safety: tube-terminations!

Jon March

Member
1) There is an up & down, sharply angled 3/4" tube on the manifold side of the block on these cars - with an open directed to the bilge on earlier cars, and pinched off on later ones
a) wtf is it?
b) can it please be cut back and capped?! (at least on later ones where its pinched? ....or is it some sort of emergency overflow that somehow re-opens the end-crimp back up in a some sort of over-pressure event?

I would like to cut it back and cap it off neatly of its not used - its original...but its unsightly in my view, and in addition i dont want a messy bilge any more than i need to have if its really not necessary


2) re: the S-shaped, carb-boilover evap-tube on the manifold (fed by a pinhole in the manifold below the carb that needs to be kept open)

I agree with Gord that its stupid to design fuel to dump into the bilge - even if 99% of the time it never does,, and just evaporates off by boiling in that tube. Just scary in a closed bilge. Gord mentions routing those tube-fumes to the air intake -Im imagining one would need a fitting of some kind to attach the hose he recommens to the air cleaner intake hose...ideally, with an L or J shaped elbow inside the air intake, with the opening toward the carb, to help "draw" the vapors or fuel in) - Gord, can you comment or post a detail-pic of it?

(OR - for those with later cars that have the 3/8" oil-vapor/"PCV" intake tube at the bottom of the aircleaner mount, could this fuel-boilover-return be Y'd into it?? - or is it a bad idea to introduce a way for fuel vapor to get into the valve area?


3) I think i recall seeing people delete the clunky square flame arrestor -
a) is it ok to do? (i know its solely the owners final decision whether to do this)
b) if deleted - how do you attach the air cleaner base to the top of the carb - the air cleaner opening is a little larger, eliminating any slide-on fit (nor setscrew) to affix it
?
how to do??


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SNOWBIRD

Amphicar Expert
If your car has the hose from Valve cover to carb, you do not need the vent tube it can be blocked off right at the block,,
If valve cover dose not have the hose you MUST have the Vent into bottom of Blige., Again it originally would be in a car that had air blowing by it as it went down the road sucking fumes out and onto road. intake is the screened oil filler cap.
 

jfriese

Active Member
Gord,

Just a question, since both my cars vent from the valve cover I didn't run into this but why wouldn't blow by be okay going out the oil filler cap? Perhaps a bit messy if you have a lot of blow-by, but I wouldn't think it would hurt anything. Having an open vent tube would just dump the mist into the bilge anyway. Seems pretty much the same.

My cars, with the vent tubes coming from the valve cover, get run hard on the California freeways and that later tube system dumps blow-by garbage into the intake side of the air cleaner. With hard driving this tended to dirty the air cleaner fairly often. I guess Amphicar worked out this system before Positive Crankcase Valves came along. I plumbed in an "oil catch can" into the line to get the worse of the blow-by oil trapped before it hit the air cleaner. I put a drain on the bottom to occasionally drain off this oil. That has worked fine for years now.

John Friese
67 White
67 Red
 
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SNOWBIRD

Amphicar Expert
The car motor needs to breath, to get rid of fumes(explosive) So air come in threw the oil filler cap and was sucked out by DRAFT of the air going by that tube under a car going down the road(not so in Amphicar) motor in piv has no hose on Valve cover so tube must be open.
Yes our pre PVC system sucks it into motor from hose on Valve cover and in threw Oil Cap. so they do not need the lower tube at all, it can be removed and plugged on these engines.

Chucks Motor 002.JPG
 

Jon March

Member
The catch can is a nice addition you did!

But im confused on airflow- help me here

on early cars - air would come in the breather style oil cap, and out thru the V-tube

on later cars - the v-tube is defeated - oil instead exits thru the tube on the valvecover - but i thought that later cars had the tight-fitting, non-breather cap...
...so how does air get into the later motors motor to create "flow" like the earlier ones?
 

jfriese

Active Member
Engines only need air to flow into the carb. and nowhere else. Gas buildup inside the crankcase is from air that gets past the piston rings (blow-by) during operation. The harder you push the engine, and the poorer the piston ring fitting, the more gas and oil mist will be created. That indeed is what that down pipe (draft tube) was for in a regular car. As the car moved, air going past that open tube would allow the crankcase blow-by gases and oil mist to get out. Many Amphicars just let that stuff exit into the bilge. Somewhere along the line they decided to close off that tube, to keep the bilge cleaner I suppose, and vent that stuff from the valve cover into the air cleaner. The way Amphicar did it rather quickly fouled the air cleaner element with oil mist. I added an "oil catch can" into the line to strip the oil mist out from that air and keep it from fouling the filter. Sometime in the 60's car makers came up with a valve that would allow these gases to be injected into the engine when it was running fast and essentially shut off the line when running slow, to avoid messing up the air fuel mixture. This was called a PCV valve, for "Positive Crankcase Ventilation". For decades now some form of this system has been used by car manufacturers. Adding a PCV valve to an Amphicar is a bit of a hassle but adding an oil catch can to cars with closed off draft tubes is quite easy. And yes, cars with that closed system have a sealed type oil filler cap. In a perfect engine with perfect piston ring seals there would be no blow by gases and thus no need for any of this stuff. There never has been an engine this perfect though.

John Friese
67 White
67 Red
 
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